Principal Fluid Systems Engineer

ABOUT FIREFLY AEROSPACEFirefly Aerospace is a space and defense technology company on a mission to reliably and repeatedly launch, land, and operate space systems from Earth to the Moon and beyond. As the partner of choice for critical space missions, Firefly is the first commercial company to launch a satellite to orbit with 24-hour notice and the first company to achieve a successful Moon landing. Headquartered in north Austin, Texas, Firefly is looking for passionate, hardworking innovators to join our team and help fuel our successful trajectory into space. SUMMARYThe Fluid Systems team at Firefly Aerospace is responsible for all fluid subsystems across our launch vehicles and spacecraft, including our Blue Ghost Lunar Lander and Eclipse Launch Vehicle. As a Principal Propulsion Engineer, youll own the design, development, integration, test, and qualification of flight fluid systems. Working closely with engineering, manufacturing, and integration teams to iterate, answer questions, and close feedback loops.This role blends deep technical ownership with cross-functional collaboration, serving as both an individual contributor and a technical mentor. The ideal candidate thrives in fast-paced, hardware-rich environments, embracing new challenges with grit, creativity, and accountability. Were looking for engineers who are excited to roll up their sleeves and help define the future of space transportation.RESPONSIBILITIES Own and lead the full lifecycle development of flight fluid systemsfrom concept through launch and operation. Develop architectures that improve reliability, simplify manufacturing, and reduce cost and schedule risk. Define system requirements and interface definitions for propulsion, pressurization, venting, purging, fill/drain, and other fluidic subsystems. Execute detailed designs using CAD and analytical tools, and coordinate closely with thermal, structural, systems, and integration teams. Oversee qualification and acceptance test campaigns, including procedure development, test execution, and data review. Lead technical risk trades, anomaly investigations, and corrective actions across engineering and production. Mentor early-career engineers and provide technical reviews of hardware designs, analysis, and test plans. Serve as the discipline owner in program architecture discussions and influence long-term roadmap for in-space servicing and reusability.QUALIFICATIONSRequired Bachelors degree in Mechanical, Aerospace Engineering, or a related field. 10+ years of experience in aerospace fluid systems or propulsion. Proven ownership of a subsystem or major fluid component through design, build, and test. Strong technical foundation in pressurized systems, cryogenics, high-pressure gas, and propellant feed design. Proficiency in CAD, P&ID creation, and familiarity with ASME Y14.5 and aerospace standards. Experience conducting system-level analysis, risk trades, and root cause investigations. Excellent communication and collaboration skills across engineering and production teams.Desired Advanced degree (MS or PhD) in engineering discipline. Demonstrated hands-on experience with hardware; including fluid test hardware and instrumentation Familiarity with in-space propulsion, NASA standards, and range safety (91-710) Experience with analytical tools such as GFSSP, Python, REFPROP, or thermal/fluid modeling. Experience working with hypergolic bi-propellants Understanding of propulsion engine cycles and integration with fluid systems. History of developing flexible solutions with partially defined requirements and changing criteria Ability to present technical content to internal and external review boards.Firefly offers outstanding benefits for our employees, including generous health, dental and vision plans with low plan deductibles, parental leave, educational reimbursement, short term disability, and flexible PTO options. To conform to U.S. Government space technology export regulations, including the International Traffic in Arms Regulations (ITAR) you must be a U.S. citizen, lawful permanent resident of the U.S., protected individual as defined by 8 U.S.C. 1324b(a)(3), or eligible to obtain the required authorizations from the U.S. Department of State. Firefly Aerospace, Inc. is an Equal Opportunity Employer; employment with Firefly is governed based on merit, competence and qualifications and will not be influenced in any manner by race, color, religion, gender, national origin/ethnicity, veteran status, disability status, age, sexual orientation, gender identity, marital status, mental or physical disability or any other legally protected status.Department: Propulsion Engineering Location: Cedar park, TX